The object of the proposed work is to study problems in developmental biology with the methods of somatic cell genetics. Specifically, our aim is to develop biochemical selection systems for "luxury" products. In order to study differentiated end products, we will employ a new method, termed bioautography, which has recently been described by this laboratory. With this system, many isozymes which could not previously be visualized can now be studied. Bioautography involves the use of "microbial reagent" to visualize mammalian enzymes after gel electrophoresis. With the aid of bioautography, we will map and determine the subunit structure of several differentiated end products.